The present invention relates generally to medical appliances for biomedical therapeutic applications, including osteogenesis, based on application of pulsed electromagnetic fields (PEMF), and more particularly to PEMF""s developed in a multi-coil, multi-functional PEMF therapeutic device which optimizes penetration of focussed electromagnetic fields at a treatment site for bone and soft tissue therapy.
Electricity is common in living things. In the human body, it provides the basis for thoughts, senses, movement and the rhythm of the heart. As has been learned over approximately the last 50 years, it may also play a crucial role in the functioning of the skeletal system. It is now known that bones carry electric potentials that occur when the bones are at rest. These xe2x80x9cbioelectricxe2x80x9d potentials are an inherent property of living bone. They are a product of cellular metabolism, thus they disappear when cellular death occurs. It has been shown that active growth plates are electronegative, while the mid-shaft is not. When a fracture occurs, that site also becomes negative and is accompanied by an increase in negativity over the farthest growth plate from the fracture. These intriguing findings lead one to believe that this negative electrical state may be a signal for bone growth.
Bone becomes stronger when subjected to mechanical stress, such as walking, running, weight lifting or hard physical labor. These mechanical stresses are termed weight bearing or bone loading by rehabilitation specialists. When under stress, bone tissue deposits more of the mineral salts that lend strength to bone. When the same stress is removed, bone-resorbing cells (called osteoclasts) go to work and tear down the unnecessary bone. This is why a bone seems to shrink in size when it has been in a cast for some time. This would also partly explain the space osteoporosis that develops in astronauts during long space flights, due to the lack of bone loading in microgravity.
The principles of bone growth and fracture healing follow a process according to Wolff""s Law, named after the Orthopedic Surgeon J. Wolff, who discovered this phenomenon in the late nineteenth century. Wolff""s Law states that xe2x80x9cevery change in the form and function of bones or of their function alone is followed by certain definite changes in their configuration in accordance with mathematical laws.xe2x80x9d This principle states that a bone responds to stress by growing into whatever shape best meets the demands the body makes of it. When a bone is bent, one side is compressed and the other is stretched. When it is bent consistently in one direction, extra bone grows to strengthen the compressed side, and some is absorbed from the stretched side. This law can explain how weight bearing, athletics and the activities of daily living influence the bone structure of a tennis or baseball player, body builder, etc. The Wolff""s Law phenomenon of bone reorganization occurs because there is a stimulus to the periosteum to grow new bone at a surface where there is compressional stress, while dissolving bone where there is tensional stress.
An understanding of Wolff""s Law wasn""t reached until the early 1950s. Research done by I. Yasuda in Japan showed naturally occurring stress generated potentials (SGP""s) in bone. This shows that mechanical stress has an effect on the electrical forces in bone. He also found that when a bone is stressed it carries an electropositive charge on the convex (stretched) side, while the concave (compressed) side has an electronegative charge. Bones are made of piezoelectric crystals (calcium apatite) with electrical potential. By mechanically bending a piezoelectric crystal hard enough to deform it slightly, a pulse of current is generated through it. In effect, the pressure xe2x80x9cpopsxe2x80x9d electrons out of their places in the crystal lattice. They migrate down the compression, so the charge on the inside curve of a bent crystal is negative. The potential quickly disappears if the stress is sustained, but when it is released, an equal and opposite positive pulse appears as the electrons rebound before settling back into place.
This finding was a major step in explaining the mechanisms behind Wolff""s Law, showing that bone will remodel via deposition of new bone at areas of compression and via resorption of bone at areas of tension. After further examination, it was confirmed that areas of active growth in living bone such as epiphyseal plates and repairing areas, were electronegative when compared with less active areas.
It has also been discovered that when a bone fractures, the entire bone becomes electronegative with a peak electro-negativity at the fracture site. This is the same type of direct current that powers a low voltage battery. Since this discovery, the field of electro-biology came into prominence as a science where researchers devote their time to studying the effects of electrotherapy to promote bone growth. Areas of growth in bone have been shown to be electronegative, thereby indicating that osteoblasts are activated by negative charges. By implanting weak electrical current directly into the bone, research has demonstrated that bone formation is increased around the cathode (negative electrode) and decreased around the anode (positive electrode).
Marino and Becker (1970) associated the piezoelectric effect and growth control in bone with a mathematical formula. They demonstrated that on loading, bone will generate a bound surface charge distribution, p(xt) which is nulled by ion current in the permeating interstitial fluid. This process was monitored on a macroscopic level by measuring voltage. A symmetric biphasic pulse is seen, thereby proving the link between mechanical and electromagnetic energy in bone.
To mimic nature""s own natural healing mechanisms with electrotherapy, currents of electromagnetism (pulsating electromagnetic fields or PEMEs) are sometimes applied to bones that fail to heal properly. Electromagnetic coils are placed outside the surface of the cast creating weak electromagnetic fields directed to stimulate the fracture site. Like the piezoelectric effect, it is believed that PEMFs stimulate reproduction of bone cells responsible for producing osteogenesis.
In osteology, a callous is defined as bony an cartilaginous material forming a connecting bridge across a bone fracture during repair. Within one to two days after injury, a provisional callous forms, enveloping the fracture site. Bone-forming cells in the periosteum (the bone layer where new bone is produced) proliferate rapidly, forming collars around the ends of the fracture, which grow toward each other to unite the fragments. The definitive callous form slowly as the cartilage becomes ossified. Two to three weeks after injury, strong bony extensions (trabeculae) join the fractured bone ends, and the organized aspect of bone gradually recurs. The callous is resorbed over a period of months.
Bone growth stimulation treatment has seen some success using two main types of biophysical treatment, each of which has been shown to be beneficial in stimulating bone growth. These two types are mechanical signals and electrical signals. These biophysical signals already occur naturally in the human body. However, it is unclear which specific components of the biophysical forces acting on the bone are actually osteogenic and which are just byproducts of bone loading.
The clinical applications of mechanical signals in osteogenesis can be seen as follows. Since past research has found that bone is sensitive to biophysical stimuli induced at low frequencies, the possible role for mechanical stimulation of bone has been further investigated. It is known from past research that a range of frequencies has been shown to persist between 10 and 50 Hz in living bone. Therefore, studies were done by McLeod et al. (McLeod and Rubin, 1992) to see if low amplitude mechanical energy induced at the optimal frequency range could in fact induce an osteogenic response. It was discovered that the osteogenic potential of mechanical stimulation is very similar to electrical stimulation, being very dependent on what frequency is being used. However, the optimal frequency in mechanical signals is higher, with an increasing osteogenic potential up to 60 Hz. This was also found to be dependent on the duration of the signal.
The claims of researchers McLeod and others equating parameters of mechanical stimulation inducing osteogenic potentials in a parallel mathematical relationship to the endogenous electrical stimulation at varying frequencies over time in bone requires further investigation in order to become an exact and dependable science.
There is a clear role for biophysical treatment in the maintenance and treatment of a structurally optimized and secure skeleton, which includes the employment of bone loading and muscular activity. These biophysical stimuli have great potential in the clinical setting if used correctly. They provide a clear and efficacious alternative to pharmaceutical intervention (i.e. biphosphonates, etc), are already occurring in healthy normal bone, are safe at the low levels needed for maximal stimulation and lead to the formation of lamellar bone by going through the entire biological process of bone remodeling. In modern physical medicine terminology, Wolff""s law is the underlying basis for a concept known as Specific Adaptation to Imposed Demands (SAID).
These biophysical stimuli as discussed have demonstrated a range of frequencies and mechanical energies (signals) that stimulate osteogenesis. As far as mechanical signals go, at 1 Hz, 100 microstrains produce no response, but when the frequency is raised to 30-60 Hz, an extremely osteogenic response is felt. The case with electrical stimuli is the same. At electrical stimulation below 5 Hz, no osteogenic response is produced, however, once raised to 15 Hz, an extremely osteogenic response is observed. The bone is clearly very sensitive to the frequencies used, so therefore the optimal range of frequencies for stimulating bone must be found.
As new evidence that challenges previous assumptions comes to light, it is necessary to rethink Wolff""s Law and the old models and ideas. Historically, it has been thought that the largest effect on bone morphology comes from large biophysical signals. However, new research shows that it is the low magnitude electrical and mechanical signals that are most osteogenic when applied at the appropriate frequency.
It has been shown that bone is very responsive to the amount and rate of deformation or xe2x80x9cstrainxe2x80x9d that it is exposed to. Bone remodeling appears to be directly related to the strain that bone experiences. The question then is, xe2x80x9cHow is the strain signal actually transformed into a cellular response?xe2x80x9d Strain generated potentials (SGP""s) are a likely candidate, due to the following facts: 1) they are generated when strain is imposed and 2) potential differences have been associated with growth and repair of bone. It is also known that bone responds to cyclic loading, while a constant load will have little effect on remodeling. The fact that SGPs decay rapidly when deformation ceases supports the correlation between the two. Additionally, studies show that applying an exogenous electricity source to bone can stimulate bone deposition. In general, these studies found that when a DC current is applied, bone is deposited at the negative terminal (cathode), while bone may be resorbed at the positive terminal (anode). More recent research indicates that bone deposition can also be stimulated with alternating electrical fields, which more closely simulate functional activity.
Stimulation of bone growth has multiple applications including treatment of fresh fractures, non-union fractures, and bone disorders such as osteoporosis, and preventative uses, such as preventing bone mass loss in immobilized limbs or in low gravity situations such as outer space.
Specifically, very low frequency (15 Hz) and low intensity stimulation can be very effective at stimulating bone growth (McLeod and Rubin, 1992). It should be noted, however, that SGPs are not the only mechanism being studied as a signal for bone remodeling. One area being pursued concerns the effects on remodeling of shear forces induced by fluid flow through bone. Another area of research involves improvements in nutrient transport to bone cells that may occur during loading. It is possible that many mechanisms may contribute to the adaptations seen in bone with repetitive loading.
The use of electrical and electromagnetic therapy for stimulating growth and repair of living tissue has been known and recognized as an acceptable form of treatment for well over a century. In cases in which there has been a failure to heal, such as non-union fractures, stimulation of repair by electromagnetic fields (EMF) has been shown to upregulate gene expression for matrix proteins and to stimulate matrix synthesis thereby effecting bone repair (EMF Science Review Symposium). Matsunaga et al. (In Vivo May-June; 1996 10(3)) explains that the influence on osteogenesis of magnetic fields (measured in gauss) may be equal to or more important than the influence of electric fields (measured in Hertz). The optimum setting for electromagnetic stimulation was examined by histologically assessing the degree of osteogenesis at different settings of electromagnetic stimulation, and comparing alkaline phosphatase (ALP) activity in the bone marrow. For this experiment, an electromagnetic field generator manufactured by the Institute of Physical and Chemical Research was used. The intensity of the magnetic field was set at eight levels; 0.1, 0.2, 0.4, 1, 2, 4, 6, and 8 gauss (G). The frequencies used were 5, 10, 20, 50, 100 and 200 Hz. Pulse durations were 6, 12, 25, 50 and 100 microsec. Significant ALP elevation and osteogenesis were observed at magnetic field intensities of 0.4, 1 and 2 G. ALP activity did not differ between different frequencies. ALP activity at pulse durations of 25 and 50 microsec was significantly higher than at other pulse durations. The effect of electromagnetic stimulation on osteogenesis greatly depends on the intensity and pulse duration of the stimulation.
Currently, full advantage is not being taken of the use of these biophysical and electrical stimuli in the health care professions, due to lack of knowledge and education in this field. However, as the underlying mechanisms at the molecular and cellular level become understood, it is hoped that these stimuli will be better understood, and as a result, medical instrumentation using this medical technology will therefore become more widely implemented in the clinical and out-patient setting.
There are many prior art patents relating to osteogenesis and electromagnetic therapy of tissues, in animals and humans, using contact electrodes and non-invasively, and a general understanding of the state of the art is facilitated by review of the following patents, which are listed here to give an overview of the level of knowledge:
U.S. Pat. No. 4,266,532 to Ryaby et al./non-invasive induced voltage/tissue repair;
U.S. Pat. No. 4,456,001 to Pecastore/non-invasive/electromagnetic/bone treatment;
U.S. Pat. No. 4,467,808 to Brighton et al/non-invasive/osteoporosis treatment;
U.S. Pat. No. 4,674,482 to Waltonen et al/magnetic field/animal tissue treatment;
U.S. Pat. No. 4,683,873 to Cadossi et al/electromagnetic tissue treatment;
U.S. Pat. No. 5,290,409 to Liboff et al/electromagnetic bone tissue stimulation;
U.S. Pat. No. 5,338,286 to Abbott et al/PEMF field for bone growth stimulation;
U.S. Pat. No. 5,792,209 to Varner/electromagnetic field to decrease osteoporosis;
U.S. Pat. No. 5,825,036 to Ishikawa/EMF to increase recovery power of organs;
U.S. Pat. No. 5,880,661 to Davidson et al/complex EMF generator/bone growth;
U.S. Pat. No. 5,620,463 to Drolet/electrophysiological conditioning for healing;
U.S. Pat. No. 5,743,844 to Tepper et al/PEMF bone growth stimulator;
U.S. Pat. No. 5,891,182 to Fleming/contact electrodes for tissue regeneration;
U.S. Pat. No. 5,919,679 to Blackman et al/magnetic field acting on biological system;
U.S. Pat. No. 5,951,459 to Blackwell/PEMF coil for treating injuries/bone healing;
U.S. Pat. No. 5,997,464 to Blackwell/PEMF coil for treating injuries/bone healing;
U.S. Pat. No. 6,029,090 to Herbst/multi-functional electrical stimulation signals.
As shown in the above list, prior art EMF devices have utilized both invasive implantation (direct stimulationxe2x80x94as disclosed in U.S. Pat. No. RE35,129 to Pethica et al.) and non-invasive magnetic fields. Clearly, a non-invasive procedure is preferable, being painless to the patient and not requiring a hospital stay. Additionally, surgery introduces the possibility of infection. Direct stimulation requires the patient to undergo surgery twice, once upon implantation and once for removal. Although non-invasive devices are therefore usually preferable, prior art non-invasive devices have been limited in their ability to simultaneously become part of or imbedded into an orthopedic brace and treat a fracture site, and have generally achieved this only where a single coil is involved.
Furthermore, the previously known devices did not provide for multiple treatment protocols. In the case of fractures, it is often desirable to begin treatment while a cast is in place and to continue treatment after the cast has been removed. However, this requires two different apparatuses or type of coils, one to be used with the cast and one without the cast.
U.S. Pat. No. 4,616,629 to Moore shows a magnetic coil embedded in an orthopedic cast and U.S. Pat. No. 4,574,809 to Talish et al. describes another form of cast-embeddable coil for electromagnetic therapy. These last two mentioned patents utilize a conventional cast with a removable plug-in connection for a pulse-signal generator. However, these devices are not portable and must be used with a conventional plaster or fiberglass cast.
U.S. Pat. No. 4,066,065 to Kraus recites a jacketing mass that may be provided as a ridged support surface with windings of a coil embedded therein. The Kraus patent has only a single elliptical cylinder-shaped coil.
U.S. Pat. No. 5,344,384 to Ostrow, one of the co-inventors of the present invention, discloses a magnetotherapy apparatus designed as an applicator wrap to be placed around an injured body member to provide a brace, and having magnetic coils for generating an electromagnetic field applied to a target area for tissue therapy.
Japanese Patent published as PCT publication WO85/01881 to Onishi, discloses a magnetic field therapeutic appliance arranged as a plurality of housings each having a magnetic field generator joined together and wrapped over a body part, but no multi-functional applications are described, such as a wrap immobilization function.
Prior art devices attempting osteogenesis include the electromagnetic apparatus disclosed in U.S. Pat. No. 5,014,699 to Pollack et al, where a transducer is placed over a previously formed plaster cast, and is not independently supported. Similarly, the multi-conductor ribbon cable treatment shown in U.S. Pat. No. 4,993,413 to McLeod et al. and the flat bands described in U.S. Pat. No. 4,757,804 to Griffith et al., does not provide an orthotic support. Furthermore, the magnetic fields generated by the aforementioned apparatus are not directionally oriented perpendicularly with respect to a target area. Although the apparatus shown in U.S. Pat. No. 5,100,373 to Liboff et al generates normally directed magnetic fields from two treatment heads, the heads are not positioned for advantageously combining magnetic flux.
Despite the above-mentioned advantages of PEMF treatment, the potential dangers of overexposure to EMF are being explored by government agencies worldwide. Therefore, it would be desirable to provide a device that could best focus the field on the treatment site without exposing large areas of the body to unnecessary EMF""s. Medical devices that use PEMFs are regulated for human use by the FDA and other regulatory governing bodies, and are usually regarded as a safe alternative to or as an adjunct to surgical intervention.
PEMFs (pulsed EMF""s) represent a relatively complex signal in comparison to simple sinusoidal exposures. PEMF waveforms typically consist of short bursts of narrow pulses in the range of 15-75 Hz. However, waveforms of this type do not penetrate biological tissue efficiently.
Cakirgil et al. in Orthopedics (November 1989 Vol.12/No. 11) compares two-coiled and four-coiled systems for PEMF treatment and concludes that a four-coil system using two perpendicular magnetic fields provides a more effective PEMF treatment. However, the disadvantages of the prior art systems make it an unlikely choice. The existing four coil systems are large and immobile and xe2x80x9crequire a new design.xe2x80x9d The four-coil system used by Cakargil cannot be adjusted. Additionally, there is interference between the two perpendicular magnetic fields. The system used by Cakirgil is not within the acceptable FDA boundaries, limits and levels for field strength dosages for safe treatment.
In the technical paper published in NASA technical reports, document ID: 19940027240 N, 94N31746, the role of PEMF fields were investigated as a method of muscle stimulation to alleviate the effects of suspension via unloading muscle and bone.
In the Journal of Orthopedic Sports Physical Therapy (1993), the April 17 issue contains a paper by D. P. Currier et al describing a new method of neuromuscular stimulation using PEMF stimulation for reducing girth loss, pain and muscle weakness.
Thus, it would be desirable to provide a multi-functional osteogenesis device that would provide a portable modular magnetotherapy apparatus which could be removably incorporated within a cast or orthotic brace or preform and that would allow for multiple arrangement and directionality of the electromagnets so as to provide pulsed electromagnetic fields directionally oriented perpendicular to the target area for better focus and penetration at the treatment site.
Accordingly, it is a primary object of the present invention to provide a. medical appliance for biomedical therapeutic applications, including osteogenesis, based on application of pulsed electromagnetic fields (PEMF), and more particularly to PEMF fields developed in a multi-coil, multi-functional PEMF device which optimizes penetration of focussed electromagnetic fields at a treatment site for bone and soft tissue therapy.
It is another object of the present invention to provide a multi-functional, modular osteogenesis device using small electromagnetic coils that create a high magnetic flux penetration into bone tissue for treatment of fractures and osteoporosis.
It is a further object of the invention to provide sequentially activated coils and a rotating cylindrical energy field focussed at a target area so as to stimulate bone growth. Saturation of the magnetic field is achieved through orthogonal placement of the coils.
It is yet a further object of the invention to provide a waveform composed of a carrier wave and a treatment wave for optimal penetration of biological tissue.
It is a still further object of the invention to provide an osteogenesis device which may be used alone or in combination with a cast, brace or pre-form with adjustable modular coils for use under, over or within a cast, brace, splint or pre-form.
It is yet another object of the invention to provide PEMF neuromuscular stimulation for reducing muscle atrophy as a countermeasure to body unloading effects.
It is yet another further object of the invention to combine PEMF stimulation with a method of splinting, casting or bracing a body part, which is commercially identified by the inventors as the STIM-SPLINT concept.
In accordance with a preferred embodiment of the present invention, there is provided a PEMF biophysical stimulation field generator device comprising:
at least two pairs of electromagnetic coils, individual ones of each pair being arranged at the respective opposite ends of a pair of orthogonal axes;
means for generating a pulsed activation signal applied simultaneously to individual ones of said oppositely arranged coil pair so as to produce oppositely-directed pulsed electromagnetic fields, and subsequently to the other of said oppositely-arranged coil pair, in sequential, alternating fashion, said activation signal having a random frequency component,
wherein said activation signal provides PEMF stimulation comprising a relatively high frequency carrier wave amplitude-modulated by a relatively low frequency treatment wave,
and wherein said amplitude-modulation introduces a random frequency pattern.
In accordance with a preferred embodiment of the biophysical stimulation signal device of the present invention, a multi-functional therapeutic garment or pre-form wrap is provided containing a plurality of small magnetizing coils, with the pre-form wrap being shaped for placement circumferentially around the body part containing the fracture site. By virtue of its modular design, the pre-form wrap may be opened and the coils removed and placed in, over or under a cast, and the coils may be removably provided in the pre-form wrap containing a portable power source. The electromagnetic coils are aimed at the fracture site in perpendicular relation to the body surface. The perpendicular placement of the coils circumferentially around the treatment site creates a cylinder of treatment and insures maximum focussing of the energy to the treatment site. The electromagnetic coil has a central ferrite core for use with high frequency applications to secure a homogeneous magnetic field. The resulting magnetic fields generated in the device cumulatively interact for deeper magnetic flux penetration to the treatment site.
The coils generate an electromagnetic field (PEMF type) when an activation signal is applied to them, and in accordance with the inventive technique, the activation signal is a combination of a high frequency carrier wave that is amplitude modulated by a low frequency treatment wave. The field generated by the coils is referred to herein as a stimulation field, which reflects the activation signal and carries its waveform directly to the target area, which is the treatment site.
For osteogenesis applications, this multi-coil configuration has been shown to be superior to prior art two-coil systems (per Cakirgil et al., as mentioned in the Background). The coils are designed to apply pulsed, adjustable, low-strength electromagnetic field signals, sufficient to optimally affect specifically targeted fractures, providing enhanced and improved focussed depth penetration to the body tissues to which it is applied. The coils are sequentially activated with coils on the same axis generating oppositely directed electromagnetic fields. Pulsing of the coils is done on alternate axes thereby generating rotational fields.
Unlike the bulky, stationary four coil system of Cakargil, the fast duty cycle of alternating on/off between the dual perpendicular electro-magnets of the present invention does not interfere with the dual planes of PEMF""s since they are not used simultaneously. When the dual perpendicular planes of PEMF therapy are applied at fast pulsating rates, a moving energy field in a cylinder of treatment is thus established with a greater saturation gradient of magnetic flux and fields to the treatment site. The electromagnets used in the present invention are smaller than those of the prior art and provide greater, improved therapeutic effects, which will be explained further herein. Further, the electromagnets of the present invention may be adjusted as desired, since they are lightweight and mobile, and do not interfere with the activity of daily living (ADL).
The biophysical stimulation field generator device of the present invention applies an athermal pulsed high frequency homogenous field with combined homogenous AC/DC electromagnetic fields using gauss levels between 2-3 gauss with alternating square wave frequencies varying from 10-30 Hz. The pulsed electromagnetic fields employed in the present invention carry the PEMF stimulation developed by the activation signal to create the least amount of impedance to the body. This configuration, when combined, conveys optimum focussing of the treatment.
In the instant invention, the high frequency carrier wave maintains and increases better depth penetration of the electromagnetic field at the treatment site, allowing the low frequency, which is the actual treatment frequency, to achieve maximum flux depth penetration. The biological tissue is not sensitive to the high frequency carrier wave but reacts to the low frequency wave, thereby naturally filtering the amplitude modulation of the carrier wave with the treatment wave. The energy employed has an athermal effect with duty cycles, by way of example, at 5-30 msec. on and 5-30 msec. off. Optimally, 20 msec is used in the present invention. A 50% duty cycle is applied in the preferred embodiment. The activation signal has an interval frequency of 25 Hz/10 KHz (sinusoidal) with a current level of 5 mAmp. When these parameters and frequencies are combined, a homogenous field is developed at the treatment site.
In the osteogenesis application, three factors in the design of the inventive activation signal, when combined and integrated for the particular application, provide the optimum parameters responsible to induce maximum physiologic and therapeutic effects, and help to minimize the undesired effects of magnetic fields on living tissue: the small magnetizing coils which prevent the dispersion of the electromagnetic field to adjacent tissues; the carrier frequency which is responsible for a marked improvement in the concentration of the magnetic field at the treatment site; and the phasic stimulation which improves the electromagnetic beam concentration in the center, further eliminating electromagnetic field dispersion.
Also in accordance with the principles of the invention, the PEMF stimulation develops an electrical field in muscle tissue. This electrical field developed by the electromagnetic field causes tetanic microcontractions of muscle tissue, and stimulates the neuromuscular junction, thereby offsetting muscle atrophy, a common side effect of immobilization. The microcontractions, which create gentle exercise loading simultaneously induce and/or enhance bone growth stimulation. When a limb is immobilized in a cast or brace or is in a low gravity environment, the unloaded bone is unstimulated due to lack of biophysical and bioelectrical signals. The device of the present invention generates an activation signal that introduces an osteogenic response mimicking the endogenous signals that result from naturally occurring mechanotransduction which stimulates bone growth. One of the signals for induction of mechanotransduction is the gravisensing process of the body. The activation signal generated by the device of the present invention in combination with other features of the device act as an electrobiophysical signal, replacing the normal body stimulus, to promote similar effects accomplished by bone loading.
To mimic the effects of bone loading, the inventive activation signal generates a similar piezoelectric effect on the bone surface to substitute or provide similar signals when the mechanical force is applied. This generated piezoelectric potential may cause molecular binding of bone minerals.
The anticipated shorter healing and rehabilitation time resulting from the application of the present invention, along with the reduced muscle atrophy enables the patient to return to normal activity sooner, while reducing the number of clinic visits required after cast removal.
While not wishing to be bound by theory, it is believed that callous formation and new bone formation of the fractured bone is a result of the inventive activation signal and the electrical potentials created, rather than the direct magnetic field effect (B/H) of the diamagnetic material.
The development of a transverse electric field in a solid material when it carries an electric current and is placed in a magnetic field perpendicular to the current, creates an electrical charge in the tissues that develops bone growth stimulation. This is based on the Hall effect, which is a result of the force that the magnetic field exerts on the moving positive or negative ions that constitute the electric current. Whether the current generated comprises the movement of positive ions, negative ions in the opposite direction, or a mixture of the two, a perpendicular magnetic field displaces the moving electric charges in the same direction sideways at right angles to both the magnetic field and the direction of current flow.
The accumulation of charge on one side of the conductor (i.e. bone) leaves the other side oppositely charged and produces a difference of potential. This phenomenon may be detected by an appropriate meter to read this difference in potential as either a positive or negative voltage, known as the Hall voltage. The sign of this Hall voltage determines whether positive or negative ions are carrying the current. In summary, the magnetic field produces an electric field, and current as per the Maxwell/Lenz laws.
Medical indications that would benefit from using the osteogenesis device of the present invention include osteoporosis, arthritis and others. Additionally, the osteogenesis device can be used for prevention of space osteoporosis.
The combination and integration of all the parameters and properties of the invention as described herein, and other features and advantages of the invention, will become apparent from the following drawings and description.